#include<iostream>
using namespace std;
class Sum
{
public:
	Sum()
	{
		_sum += _cnt;
		_cnt++;
	}
	static void Init()
	{
		_sum = 0;
		_cnt = 1;
	}
	
	static int getSum()
	{
		return _sum;
	}
	
private:
	static int _cnt;
	static int _sum;
};

int Sum::_cnt = 1;
int Sum::_sum = 0;
class Solution
{
public:
	int Sum_Solution(int n)
	{
		Sum::Init();
		Sum* p = new Sum[n];
		return Sum::getSum();
	}
};
int main()
{
	Solution st;
	cout << st.Sum_Solution(5) << endl;
	return 0;
}